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JASON Scientists Not Convinced RRW Could Be Certified without Nuclear Testing

Panel recommends additional experiments, more transparent peer review process

 A report by the JASON defense science panel provides another reason to halt the Reliable Replacement Warhead (RRW) program. JASON is a group of independent scientists that advises the government on technical defense issues. At the request of Congress, the group reviewed the proposed design for the first replacement warhead, now designated WR1. The panel was "not yet assured" that there will be sufficient evidence that the warhead can be formally certified as suitable for deploy­ment without conducting nuclear explosive tests.[1] JASON also found that the warhead certification plan needs further work, including the design and development of additional non-nuclear tests.

As required by Congress, any replacement nuclear warheads must be designed, produced and certified for use without explosive testing. Previously, all U.S. nuclear warhead designs that have been formally certified have undergone a series of nuclear explosive "proof" tests before they entered the stockpile. The United States has not developed a new warhead since 1989, nor conducted a nuclear explosive weapons test since 1992.

The JASON panel also urged that the warhead certification plan be made more transparent and independent of the Lawrence Livermore National Laboratory, which is tasked to design and develop the weapon.

JASON was not tasked with evaluating the relative merits of the RRW program and the methods currently used to maintain the arsenal in the absence of nuclear testing. In fact, there is no technical justification for a replacement warhead. Many independent technical studies, including previous reports by JASON and the National Academy of Sciences, have concluded the current Stockpile Stewardship and Life Extension programs can continue to maintain the current U.S. nuclear stockpile as safe, secure, and highly reliable for many more decades.

The new design introduces new uncertainties

The WR1 warhead is intended to replace the 100-kiloton W76 warhead currently deployed on U.S. Trident submarine-launched ballistic missiles. According to the Department of Energy (DOE), the new warhead is similar in design to a previously tested warhead that is well understood. On this basis, the DOE asserts the new warhead can be certified without nuclear explosive testing.

However, the core nuclear components (which constitute the "Nuclear Explosive Package") have been changed in at least three significant ways.

The first change is intended to increase the "performance margins" of the warhead so that   the warhead will detonate with the desired explosive yield even if its properties change as it ages. (However, the concern about aging relates to the plutonium core of U.S. weapons, and recent experiments conducted by the weapons laboratories indicate that plutonium aging will not be a problem for at least 85 years, and possibly much longer.) Although the details remain classified, it is likely that additional plutonium has been added to the primary "pit" that initiates the nuclear explosion. A second design change is intended to improve the safety of the warhead, so that its chemical high explosive does not accidentally detonate in a high-temperature fire or impact. To do so, the new design likely uses so-called "insensitive" high explosives. A third design change is said to improve the security of the warhead, to prevent its detonation by an unauthorized user or in the event it is stolen. The weapons laboratories have advertised that the design includes new and unique security features that make unauthorized detonation of the warhead virtually impossible.

In addition, the new design will eliminate the use of beryllium, which surrounds the plutonium pit. Beryllium is hazardous to the people manufacturing the warheads and to the environment, and another material will replace it. The weapons laboratories will also use new manufacturing processes to produce the plutonium pit for the WR1.

Additional research recommended by JASON would take several years

As with any complex device, the planned design changes would introduce new and perhaps unexpected uncertainties. Without conducting a nuclear test, these uncertainties could reduce confidence in the performance of the new warhead.

To reduce these uncertainties, the JASON panel  recommended that the weapons design laboratories conduct additional analyses and non-nuclear experiments, particularly to explore potential "failure modes" of the new design and to under­stand the limitations of the computer simulations that will be used as part of the certification process. The panel was especially concerned that new design features intended to prevent unauthorized use of the warhead, so-called "surety mechanisms," are poorly understood. The panel noted, "Substantial work remains on the physical understanding of the surety mechanisms that are of high priority to the RRW program."

It will likely take several years for the weapons laboratories to carry out this additional work, which is required to inform a decision about whether the new design can eventually be certified without nuclear explosive testing.

JASON calls for an expanded and more transparent peer review process

The JASON panel was especially concerned that the current peer review process for warhead certification is not sufficient. They urged it be made more transparent and independent of Lawrence Livermore National Laboratory (LLNL), which will design and develop the weapon. The panel noted, "Peer review for RRW certification must play a larger role than provided by current NNSA [National Nuclear Security Agency] guidelines, or envisaged in the LLNL plans presented to us." It added that the peer review process must be more "visible, funded and administered to assure the nation that all expertise available has been applied to a rigorous evaluation of the new design."

1 Although the complete JASON report remains classified, an unclassified executive summary has become available: JASON report, "Reliable Replacement Warhead, Executive Summary," JSR-07-336E, September 2007, available at

For more information, contact Stephen Young, Washington Representative at or 202-331-5429.

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